The present invention relates to a finishing device for sets of sheets received from a document creating apparatus, such as a copier or printer and, more particularly, to an improved finishing device having a sheet guiding and buffering mechanism that enables full productivity for compiling without interruption of document creation, redundant compiling stations, or skipping of pitches.
Many finishing devices and sheet stacking devices are known in the sheet handling equipment industry, involving collating or stacking of sheets into sets of sheets and finishing each set of sheets by stapling or binding prior to depositing the finished sets of sheets on a collection tray. In the general prior art devices, the finishing operation on the compiled sets of sheets is accomplished following the completion of the successive sets of sheets in a subsequent finishing operation. Thus, the rate of speed at which the finishing device operates is adversely effected because all of collective functions of a finishing device, such as, for example, collection of sets, stapling of sets, and the deposition of stapled sets, are all performed in sequence. This results in loss of time for the performance of the several independent finishing device functions.
The solution-for the loss of productivity has been approached in the prior art on several fronts. One solution was to provide multiple redundant compiling stations, so when one set of sheets is being finished, the subsequent set of sheets is being directed to and compiled on a different compiling station. Another solution was to skip pitches in the document creating device, so that there was a time delay between sets of sheets received by the finishing device. The preferred solution to prevent loss of productivity by a finishing device, especially for a finishing device for a high volume copier or printer, is to provide a means for buffering or temporarily storing the sheets of subsequent sets of sheets in the finishing device. The following examples are attempts to provide a type of buffering in a finishing device.
U.S. Pat. No. 5,649,695 discloses a sheet stacker and finisher apparatus in which a multi-page set of sheets delivered from a copier or printer are collected at an assembly station. During the feeding of sheets comprising the set of sheets, a jogger is actuated to align side edges and to register the trail edges against a backstop and on an assembly bar. The sheet feeding and jogging continues until a complete set of sheets has been assembled. Upon completion of a set of sheets, the feeding of further sheets from the copier or printer is interrupted until the trail edge of the set of sheets is clamped or gripped and the set of sheets removed from the assembly station. At this time a subsequent set of sheets may be fed from the copier or printer onto the assembly station, while the previous set of sheets is being stapled and then stored on a storage table. Thus, less time is lost, because the interruption in sheets being fed to the sheet stacker and finisher is only for a relatively short time and not for completion of the finishing of the prior set of sheets.
U.S. Pat. No. 6,443,450 discloses sheet stacking apparatus having one or more rotatable disks, each with one or more slots for receiving sheets therein from a copier or printer. Once the leading edge of a sheet is inserted into the slots of the disks, a controller rotates the disk to invert and deposit the sheet on a vertically movable elevator platform. The receipt of the sheets by the slots in the disk followed by rotation and deposit on the previously deposited sheets on the elevator platform is continued until the set of sheets is completed. Sheets are continually fed from the copier or printer seriatim to the sheet stacking apparatus and to prevent interruption of sheeting feeding from the copier or printer, the disk retains the subsequently deposited sheet in its slot after completion of a prior set of sheets. The disk is rotated with the sheet in its slot to receive another sheet in the same slot of the disk, so that two or more sheets are retained in the disk slot, providing time to remove the completed set of sheets. As soon as the completed set of sheets is removed, the accumulated two or more sheets in the disk slot are removed and deposited on the elevator platform. Accordingly, buffering is provided at the cost of additional volume or space in the sheet stacker to accommodate the disks and with the added problem of sheet curl and sheet marking by the slots.
Though some of the prior art sheet stacking and finishing devices provide some improved productivity, none of the prior art sheet handling devices provide a full productivity, low-cost guiding and buffering mechanism suitable for high volume finishing which utilizes a minimum footprint or space requirement and which provides a guiding sheet path to handle sheets with down curl and weak sheet beam strength.
It is an object of the present invention to provide an improved low cost sheet guiding and buffering mechanism for a finishing device that enables full productivity for compiling and finishing sets of sheets received from a high volume document creating apparatus, such as a copier or printer.
It is another object of the invention to provide a sheet guiding and buffering mechanism for a finishing device that is located in the space between a sheet transport that receives the sheets seriatim from a document creating apparatus and a compiling and finishing tray, the guiding and buffering mechanism comprising two parallel retractable arms having a slight curvature that receives sheets from the sheet transport, guides the sheets, and retracts to drop the individually received sheets one at a time onto the compiling and finishing tray, but when the last sheet of a set is dropped, subsequently received sheets of the next set of sheets is retained on the arms until the previous set of sheets has been compiled, finished, and ejected from the tray.
In one aspect, of the invention, there is provided a finishing device for sets of sheets received from a document creating apparatus, comprising: a sheet transport assembly for receiving and transporting sheets from the document creating apparatus along a sheet process direction; a sheet guiding and buffering mechanism comprising two retractable arms, said arms being positioned adjacent each other at a location to receive sheets from the transport assembly, said arms being retracted in a direction away from and towards each other, said arms being located below and substantially parallel to said transport assembly; means for retracting and returning said arms along a path parallel to said transport assembly and perpendicular to said sheet process direction, whereby said arms vertically drop the sheets therefrom when the arms are retracted; a compiling and finishing platform for receiving the sheets dropped from the arms one on top of the other to form a stacked set of sheets, said platform having means to finish and eject the stacked set of finished sheets thereon; and said arms being retracted to deliver each sheet of a set of sheets individually to the compiling and finishing platform, once the last sheet of a set of sheets is delivered to the compiling and finishing platform, said arms remain in the location to receive sheets from the transport assembly to collect the first few sheets of the next incoming set of sheets, thereby providing a buffering cycle to enable time for the previous set of sheets to be finished and ejected to a collection tray, said arms being retracted to drop the accumulated first few sheets of the subsequent set of sheets onto said platform as soon as the previous set of sheets is finished and ejected.